do floating average of people present. OMG in bash? how dare you?

scripts/peoplecounter-realtime.sh

@@ -1,27 +1,77 @@
 #!/bin/bash
 #update peoplecounter number in realtime
 #but: this is too intrusive. should only update when the count of 
-@ people has not changed for a certain time
+# people has not changed for a certain time
+if [ "$(basename $0)" = "peoplecounter-realtime-dev.sh" ]
+then  # switch between dev and prod config dynamically by script name
+  DEV="-dev" 
+else
+  DEV=""
+fi
+STATSFILE="/run/peoplecounter$DEV"
+SAMPLES=12 # how many records to keep in file
+INTERVAL=10 # how long to wait between polls
+MAXFILE="/run/peoplecountermax$DEV"
+PRESENCY="/run/presency$DEV"   # value shown on website
+# /run/peoplecounter lists all recent reads, newest at end
+# let's have some management functions instead of a database
+if [ ! -f "$STATSFILE" ]
+then
+  touch "$STATSFILE"
+fi
+function getmaxpeople() {
+  awk 'BEGIN {v=0}
+       $1 > v {v=$1}
+       END {print v}' "$STATSFILE"
+}
+function getaveragepeople() {
+  awk 'BEGIN {t=n=0}
+        {t+=$1
+         n++}
+       END {print int(t/n+0.4)}' "$STATSFILE"
+}
+function getlastpeople() {
+  awk 'BEGIN{v=0}
+        {v=$1}
+       END{print v}' "$STATSFILE"
+}
+function addcount() {
+  awk -v new="$1" -v samples="$SAMPLES" -v stats="$STATSFILE" '
+    BEGIN{n=0}
+      {p[++n]=$1}
+    END{
+        p[++n]=new
+        n++   # yes you can do off by 1 errors in awk
+        start=n-samples
+        if(start<1) {start=1}
+        for(i=start;i<n;i++) {
+          print p[i] > stats  # welcome to awk world
+        }
+       }
+  ' "$STATSFILE"
+}
 PEOPLECOUNTERIP=$(cat $(dirname "$0")"/peoplecounterip.txt")
 state="online"
 while true
 do
+  # scrape new value
   p="$(
     wget -qO - "http://$PEOPLECOUNTERIP/output.cgi?t=$(date +%s)" |
     sed 's/.*Occupancy://'|
     awk '{print $2}')"
-  if [ "$p" != "" ]
+  if [ "$p" != "" ]  # oh we got something
   then
-    oldp="$(cat /run/peoplecounter)"
+    oldp="$(getlastpeople)"
-    echo "$p" > /run/peoplecounter
+    addcount "$p"
     if [ "$p" != "$oldp" ]
     then
       logger $(basename $0) changed from $oldp to $p people
       if [ "$p" -gt "$oldp" ]
       then
-        echo "$p" > /run/peoplecountermax
+        echo "$p" > "$MAXFILE"
       fi
     fi
+    getaveragepeople > "$PRESENCY"
     if [ "$state" = "offline" ]
     then
       state="online"
@@ -34,5 +84,5 @@ do
       logger $(basename $0) people counter offline
     fi
   fi
-  sleep 10
+  sleep "$INTERVAL"
 done